Stable Compositions, Structures and Electronic Properties in K–Ga SystemsUnder Pressure**Supported by the Shandong-Provincial Science Foundation (ZR2018PA010, ZR2017BA020, ZR2017BA012, ZR2019MA054 and2019KJJ020), and the National Natural Science Foundation of China (11704220, 11674122, 11804184, 1180418 and 11974208).

Abstract

New stable stoichiometries in K–Ga systems are firstly investigated up to 100 GPa by the unbiased structure searching techniques. Six novel compositions as K4Ga, K3Ga, K2Ga, KGa, KGa2 and KGa4 are found to be thermodynamically stable under pressure. Most of the predicted stable phases exhibit metallic character, while the KGa phase behaves as a semiconductor with a bandgap ∼1.62 eV. Notably, the gallium atoms exhibit different interesting morphologies; e.g., Ga2 units, zigzag chains, six rings and cage. We further investigate the bonding nature of K–Ga systems with help of electron localization function and Bader charge analyses. Strong covalent bonding characteristics are found between the Ga and Ga atoms, and ionic bonding patterns are observed between the K and Ga atoms. Meanwhile, we notice charge transferring from the K atom to the Ga atom in the K–Ga systems. The present results can be helpful for understanding the diverse structures and properties of K–Ga binary compounds at high pressures.